[dpdk-stable] patch 'net/virtio-user: fix deadlock in memory events callback' has been queued to stable release 18.08.1

[Kevin Traynor]

Hi,

FYI, your patch has been queued to stable release 18.08.1

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 11/23/18. So please
shout if anyone has objections.

Also note that after the patch there's a diff of the upstream commit vs the patch applied
to the branch. If the code is different (ie: not only metadata diffs), due for example to
a change in context or macro names, please double check it.

Thanks.

Kevin Traynor

---
>From 9a3059147371629a60cd19ce9cd78643616de9ae Mon Sep 17 00:00:00 2001
From: Tiwei Bie <tiwei.bie at intel.com>
Date: Wed, 5 Sep 2018 12:28:50 +0800
Subject: [PATCH] net/virtio-user: fix deadlock in memory events callback
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

[ upstream commit 7ff269575bd144482d56a20fec61187f1af15dda ]

Deadlock can occur when allocating memory if a vhost-kernel
based virtio-user device is in use. To fix the deadlock,
we will take memory hotplug lock explicitly in virtio-user
when necessary, and always call the _thread_unsafe memory
functions.

Bugzilla ID: 81
Fixes: 12ecb2f63b12 ("net/virtio-user: support memory hotplug")

Reported-by: Seán Harte <seanbh at gmail.com>
Signed-off-by: Tiwei Bie <tiwei.bie at intel.com>
Tested-by: Seán Harte <seanbh at gmail.com>
Reviewed-by: Seán Harte <seanbh at gmail.com>
Reviewed-by: Anatoly Burakov <anatoly.burakov at intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin at redhat.com>
---
 drivers/net/virtio/virtio_user/vhost_kernel.c |  6 +++++-
 .../net/virtio/virtio_user/virtio_user_dev.c  | 19 +++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/drivers/net/virtio/virtio_user/vhost_kernel.c b/drivers/net/virtio/virtio_user/vhost_kernel.c
index d1be82162..a93fe5b28 100644
--- a/drivers/net/virtio/virtio_user/vhost_kernel.c
+++ b/drivers/net/virtio/virtio_user/vhost_kernel.c
@@ -116,5 +116,9 @@ prepare_vhost_memory_kernel(void)
 	wa.vm = vm;
 
-	if (rte_memseg_contig_walk(add_memory_region, &wa) < 0) {
+	/*
+	 * The memory lock has already been taken by memory subsystem
+	 * or virtio_user_start_device().
+	 */
+	if (rte_memseg_contig_walk_thread_unsafe(add_memory_region, &wa) < 0) {
 		free(vm);
 		return NULL;
diff --git a/drivers/net/virtio/virtio_user/virtio_user_dev.c b/drivers/net/virtio/virtio_user/virtio_user_dev.c
index 7df600b02..869e96f87 100644
--- a/drivers/net/virtio/virtio_user/virtio_user_dev.c
+++ b/drivers/net/virtio/virtio_user/virtio_user_dev.c
@@ -14,4 +14,6 @@
 #include <sys/stat.h>
 
+#include <rte_eal_memconfig.h>
+
 #include "vhost.h"
 #include "virtio_user_dev.h"
@@ -110,7 +112,22 @@ int
 virtio_user_start_device(struct virtio_user_dev *dev)
 {
+	struct rte_mem_config *mcfg = rte_eal_get_configuration()->mem_config;
 	uint64_t features;
 	int ret;
 
+	/*
+	 * XXX workaround!
+	 *
+	 * We need to make sure that the locks will be
+	 * taken in the correct order to avoid deadlocks.
+	 *
+	 * Before releasing this lock, this thread should
+	 * not trigger any memory hotplug events.
+	 *
+	 * This is a temporary workaround, and should be
+	 * replaced when we get proper supports from the
+	 * memory subsystem in the future.
+	 */
+	rte_rwlock_read_lock(&mcfg->memory_hotplug_lock);
 	pthread_mutex_lock(&dev->mutex);
 
@@ -153,8 +170,10 @@ virtio_user_start_device(struct virtio_user_dev *dev)
 	dev->started = true;
 	pthread_mutex_unlock(&dev->mutex);
+	rte_rwlock_read_unlock(&mcfg->memory_hotplug_lock);
 
 	return 0;
 error:
 	pthread_mutex_unlock(&dev->mutex);
+	rte_rwlock_read_unlock(&mcfg->memory_hotplug_lock);
 	/* TODO: free resource here or caller to check */
 	return -1;
-- 
2.19.0

---
  Diff of the applied patch vs upstream commit (please double-check if non-empty:
---
--- -	2018-11-20 17:53:08.832978388 +0000
+++ 0057-net-virtio-user-fix-deadlock-in-memory-events-callba.patch	2018-11-20 17:53:07.000000000 +0000
@@ -1,4 +1,4 @@
-From 7ff269575bd144482d56a20fec61187f1af15dda Mon Sep 17 00:00:00 2001
+From 9a3059147371629a60cd19ce9cd78643616de9ae Mon Sep 17 00:00:00 2001
 From: Tiwei Bie <tiwei.bie at intel.com>
 Date: Wed, 5 Sep 2018 12:28:50 +0800
 Subject: [PATCH] net/virtio-user: fix deadlock in memory events callback
@@ -6,6 +6,8 @@
 Content-Type: text/plain; charset=UTF-8
 Content-Transfer-Encoding: 8bit
 
+[ upstream commit 7ff269575bd144482d56a20fec61187f1af15dda ]
+
 Deadlock can occur when allocating memory if a vhost-kernel
 based virtio-user device is in use. To fix the deadlock,
 we will take memory hotplug lock explicitly in virtio-user
@@ -14,7 +16,6 @@
 
 Bugzilla ID: 81
 Fixes: 12ecb2f63b12 ("net/virtio-user: support memory hotplug")
-Cc: stable at dpdk.org
 
 Reported-by: Seán Harte <seanbh at gmail.com>
 Signed-off-by: Tiwei Bie <tiwei.bie at intel.com>